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Old 10-06-2012, 12:07 AM   #17626
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Originally Posted by Granpa View Post
Now I could be wrong about this, but full scale vehicle dynamics do not transfer to our little R/C cars directly. All the component sizes, weights, design etc are completely out of whack. So something as basic as sprung to unsprung ratios can sometimes not be relevant. One of the biggest problems in relating R/C cars to full scale is the rubber. Our tires have so much more grip than the full scale counterparts, what can be done on our cars would be impossible full scale.

Another factor is that our cars are so much faster, but the aero doesn't work the same cause our cars are moving more slowly thru the air. Sounds like a contradiction, but think about it.
You are sooo right.
In general the dynamics just can't be transfered.
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Old 10-06-2012, 01:38 PM   #17627
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I don't believe he was talking about rotational inertia, re: wheels/axles, but rather rotational inertia of the vehicle as a a whole.

What I'm trying to grasp still is adding weight to the rear of a car that already has a motor hanging off the back. These things launch like scalded bunnies out of the corners already and most I've seen running them locally add weight lower and further forward. Perhaps it will help stick it through the corners. I guess we'll see.
Actually I did assume it was part of the hex drive, but I see now that I was wrong. I agree with Wade's post - it should make the back end more planted, basically.

Physics apply to toy cars in exactly the same way as full size cars.
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Old 10-06-2012, 01:42 PM   #17628
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Making it part of the hex drive would be like Romney doubling down on whatever offensive statement he made this week. You might be able to get away with the first bit (extra mass) somehow, but backing it up (rotating mass) would be silly. It would also anger Big Bird.
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Old 10-06-2012, 05:25 PM   #17629
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Needing some advice/help with the following.

Raced last night trying out some tire combos. Ran first race with 55d tires front and rear and car was planted, no traction rolls. Fastest lap 25.231, Avg 25.653. Went to 60d tires up front and rolled without warning 4 times. Fastest Lap 25.070 Avg 26.914.

When I recently ran thru the day I suffered the same thing using the 60d with rollovers a feature of the day.

What set-up changes are people making when going from 55d to 60d tires. I'm thinking I should be checking ride height, but are people changing shock position or spring up front? Is it simply a matter of faster speed making driving adjustments ie slow down.

would appreciate any suggestions.
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Old 10-06-2012, 10:54 PM   #17630
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Actually I did assume it was part of the hex drive, but I see now that I was wrong. I agree with Wade's post - it should make the back end more planted, basically.

Physics apply to toy cars in exactly the same way as full size cars.
You're right, physics and the laws of physics don't change. I did not say that. What I said was that full scale vehicle dynamics often do not transfer and at times are irrelevant.

Let's just leave it at this. Read this somewhere and it seems appropriate. "For those who understand the situation, no explanation is necessary. For those who do not, no explanation is possible"
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Old 10-06-2012, 11:27 PM   #17631
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Originally Posted by aussierevo View Post
Needing some advice/help with the following.

Raced last night trying out some tire combos. Ran first race with 55d tires front and rear and car was planted, no traction rolls. Fastest lap 25.231, Avg 25.653. Went to 60d tires up front and rolled without warning 4 times. Fastest Lap 25.070 Avg 26.914.

When I recently ran thru the day I suffered the same thing using the 60d with rollovers a feature of the day.

What set-up changes are people making when going from 55d to 60d tires. I'm thinking I should be checking ride height, but are people changing shock position or spring up front? Is it simply a matter of faster speed making driving adjustments ie slow down.

would appreciate any suggestions.
This just one possibility, but frequently It is the sidewall "tucking" under and tripping the car over that is the major problem. Also, you do need to change the ride height going from one diameter to the other. If you'll compare the heights of the side wall of the 60d to the 55d, you'll see the 60d has a much taller sidewall. Layer a thin layer of cyano on the outside of the tire from the rim to the edge of the tire. In extreme cases, you may need to even extend it ti the tread or on a slick, slightly over the edge. This does two things, it stiffens the sidewall and if it does roll, you'll hit the cyano which will keep it from rolling. Usually, you only need to do the fronts, but on occasion, I've had to do both front and rear. This also works on 55d tires also. Where I race, this is an almost standard adjustment.

Another common mistake is having the car too stiffly sprung. The misconception is that to keep the car from traction rolling, the car must be kept "flat". You might try going soft with your springs and shock oils. Currently, I am running the neon yellow springs from the #53333 spring set in front and the blues in the rear from the same spring set. This seems to work on all surfaces from outdoor asphalt to indoor carpet. I am also using the light rear roll bar and have not yet experimented with the front roll bar.

Hope this helps. Many differing opinions may be presented, but this is what works for me.
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Old 10-06-2012, 11:39 PM   #17632
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Thanks for the input Granpa. The idea of the tire 'tucking' under does make sense and I will give the sidewalls some attention.

I had the car set up with white spring 35 wt oil front and 30wt oil red spring rear with light rear stablizer. The track was medium grip.

I did like how the car handled. Our track is a mix of fast sweepers and tight infield and I found the car felt planted on the 55d with this setup.

Have you had any experience with 'double stuffing' tires?. I ask simply as to me that would fill the tire and make it quite hard, so would induce understeer/push, but would help limit traction rolls?.
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Old 10-07-2012, 07:52 AM   #17633
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Originally Posted by Granpa View Post
You're right, physics and the laws of physics don't change. I did not say that. What I said was that full scale vehicle dynamics often do not transfer and at times are irrelevant.

Let's just leave it at this. Read this somewhere and it seems appropriate. "For those who understand the situation, no explanation is necessary. For those who do not, no explanation is possible"
That would defeat the purpose of anyone attending school, ever.

I think you're both right but there needs to be an adjustment to translate what one says to the other. I think what Granpa meant is that some effects (that do exist) are neglijible in a 1/10 world because of the smaller surfaces and speeds. Perhaps it's not the best way to put it, but it's not entirely wrong.

One exapmle of this is to check out the size of a TC car wing. Scaled up to lifesize would probably collapse the suspension of the car with it downforce, but in a 1/10 world it works by making up in size for what the car not make in speed.
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Old 10-07-2012, 10:22 AM   #17634
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Originally Posted by aussierevo View Post
Thanks for the input Granpa. The idea of the tire 'tucking' under does make sense and I will give the sidewalls some attention.

I had the car set up with white spring 35 wt oil front and 30wt oil red spring rear with light rear stablizer. The track was medium grip.

I did like how the car handled. Our track is a mix of fast sweepers and tight infield and I found the car felt planted on the 55d with this setup.

Have you had any experience with 'double stuffing' tires?. I ask simply as to me that would fill the tire and make it quite hard, so would induce understeer/push, but would help limit traction rolls?.
Won't comment on your set up, but it's backward from what most of us do here, except when the car is a SWB. Also the various brands of shock oils seem to vary in viscosity. 40 wt Associated is not the same as 40 wt Losi. Set ups are such an individual thing and the best set up is one that works for you. Also, the softer set up many of us have gone to, was to help with the traction rolling problems on the higher grip tracks.

Yeah, a 55d shod car will "feel" a lot more planted than a 60d shod car. I feel the it's due to the shorter sidewall allowing a less "flex" in the tire.

Double stuffing tires is a lot of trial and error. Here are a few general "rules" to which there are many exceptions. The harder the tire, the less grip it has, and the quicker responding it becomes. Double stuffing with a molded insert on the outside and inside will generally give you a tire that is too hard. A full length TC insert will work in a 60d tire, but will often give you a tire that is too hard even when backed with a foam insert. The Muchmore pink is the lone exception to this. If using a TC insert on the outside, the shorter you cut it the softer the tire. I usually used foam on the outside and a molded or cut TC insert on the inside. There are quite a few combinations you can play with.

Sorry to meander a bit, but we've been using the Spec tire for a few years. I had to meander back up memory lane for the double stuffing stuff. Rarely do it now, but did glue up a couple of sets 2 weeks ago. I used the Shimizu foam on outside and a molded Ride medium insert on the inside.

Hope this helps

Last edited by Granpa; 10-07-2012 at 10:24 AM. Reason: correction
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Old 10-07-2012, 01:58 PM   #17635
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thanks again for the information. appreciate the time taken to share your thoughts. Must get to track and practice.
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Old 10-07-2012, 06:55 PM   #17636
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I'm having an issue with my TA03 diff. When I first assemble it, the thing feels great. Its very very smooth after twisting it a few times but then starts to "grind" and then smooths back out and starts to grind again. When I first built it, it did this so I thought possibly debris, I cleaned it and started over. Same thing. I put ceramic balls in it. Same thing. Do I have a defective part somewhere in this thing?
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Old 10-07-2012, 08:10 PM   #17637
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I'm having an issue with my TA03 diff. When I first assemble it, the thing feels great. Its very very smooth after twisting it a few times but then starts to "grind" and then smooths back out and starts to grind again. When I first built it, it did this so I thought possibly debris, I cleaned it and started over. Same thing. I put ceramic balls in it. Same thing. Do I have a defective part somewhere in this thing?
Check the thrust bearing. Those do go out. I think the replacement is #53136, but that's off the top of my he'd so double check please.

Been a little under the weather the last couple of weeks, so that explains my frequent posts. Entertainment that doesn't require much energy.
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Old 10-07-2012, 09:58 PM   #17638
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Well it was a brand new diff so that could be the issue. I can loosen it up about a sixth of a turn and it goes completely smooth. Is there a such thing as too tight? I keep seeing tight diff for these things, so what exactly does this mean?
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Old 10-07-2012, 10:56 PM   #17639
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Has anyone ever seen a thrust bearing with ceramic balls? I know you can buy the balls separately, but pre assembled would work better for me.

BTW, with ceramic balls, I can crank my diff all the way down and it still works. Just a tiny bit crunchy.
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Old 10-08-2012, 03:11 AM   #17640
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Originally Posted by PROMODVETTE View Post
Well it was a brand new diff so that could be the issue. I can loosen it up about a sixth of a turn and it goes completely smooth. Is there a such thing as too tight? I keep seeing tight diff for these things, so what exactly does this mean?
I'd be tempted to take out the ceramic balls and build it with the original balls. I don't rate ceramics, they are rounder and harder but also more brittle than steel.
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